In oil-producing areas, like the south-central U.S., methane emissions may be nearly three times higher than EPA figures, university researchers found.

“It will be important to resolve that discrepancy in order to fully understand the impact of these industries on methane emissions,” lead author Scot Miller, a doctoral student at Harvard University, told Agence France-Presse.

The researchers said their figures differed significantly from the EPA’s because of their methodology.

The EPA relies on a “bottom-up” analysis that factors the amount of methane typically released by each cow, per unit of coal, or per unit of natural gas sold, the researchers said.

But the researchers used a “top-down” approach that estimated how much methane was present in the atmosphere, then tracing its sources using meteorological and statistical analysis.

If the EPA’s estimates are off by half, then the level of emission limits being placed on agriculture and industry may be rendered meaningless, according to a National Public Radio report.

The study—conducted by scientists from the U.S. and Europe—based their findings on roughly 13,000 atmospheric measurements that were taken in 2007 and 2008 from airplanes and cell towers as tall as the Empire State Building.

The researchers pointed out that methane is the second most important greenhouse gas after carbon monoxide. It traps 70 times more heat in the atmosphere than CO2 does, but remains in the atmosphere for a decade, compared to the 100 years that CO2 lasts.